1. Technical Field
The present disclosure relates generally to a light-emitting diode driver circuit and a method of operating the same, and more particularly to an integrated light-emitting diode driver circuit and a method of operating the same.
2. Description of Related Art
The power line communication (PLC) carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers. The 50/60-Hz AC power is used to be the carrier wave and then the high-frequency (about KHz or MHz) modulated single is added to the wiring system. On the contrary, the signal on the power line is decoupled to filter the 50/60-Hz AC power and then the filtered signal is demodulated and amplified. The power line communication technology is implemented without additional network lines, and the covered area of the power line communication is much larger than that of other carriers.
Reference is made to FIG. 1 which is a schematic block diagram of a related art light-emitting diode (LED) driver system of a first embodiment. The LED driver system mainly includes a light-dimming control conversion unit 10A, a light-emitting diode (LED) driver circuit 20A, and a light-emitting diode (LED) string 30A. The LED driver system receives an AC voltage Vac and converts the AC voltage Vac to drive the LED string 30A. The LED driver circuit 20A includes a power conversion unit 202A, a light-dimming control interface 204A, a constant current/constant voltage control unit 206A, and a rectifying and filtering unit 208A. In particular, the LED driver circuit 20A is integrated into a modular design but the light-dimming control conversion unit 10A is externally connected to the LED driver circuit 20A.
The light-dimming control conversion unit 10A is connected to the LED driver circuit 20A and converts a modulation signal on the AC voltage Vac to generate a constant light-dimming voltage Vdim or a PWM light-dimming signal Vpwm. In particular, the labeled “Vdim+” and “Vdim−” indicate the positive and negative terminals of the constant light-dimming voltage Vdim, respectively. Also, the light-dimming levels are adjusted according to the voltage magnitude of the constant light-dimming voltage Vdim. In addition, the labeled “Vpwm+” and “Vpwm−” indicate the positive and negative terminals of the PWM light-dimming signal Vpwm. The PWM light-dimming signal Vpwm is a digital signal with the positive and negative levels, and the light-dimming levels are adjusted according to the duty cycle of the PWM light-dimming signal Vpwm. The live wire voltage provides a live wire input voltage VLi and a live wire output voltage VLo, and the light-dimming control conversion unit 10A receives the live wire input voltage VLi and outputs the live wire output voltage VLo so that the modulation signal is acquired. Also, the live wire output voltage VLo is connected to the LED driver circuit 20A to supply power to the LED driver circuit 20A. In the conventional LED driver system, the LED driver circuit 20A has a light-dimming control interface 204A for receiving the constant light-dimming voltage Vdim generated from the light-dimming control conversion unit 10A. Also, the light-dimming control interface 204A generates the light-dimming control signal (not shown). After the constant current/constant voltage control unit 206A receives the light-dimming control signal, the LED driver circuit 20A outputs a driving voltage VLED to provide a constant-current or constant-voltage light-dimming control. In particular, the labeled “VLED+” and “VLED−” indicate the positive and negative terminals of the driving voltage VLED, respectively. In this embodiment, the light-dimming control interface 204A can be a 0-10 volt dimming control interface. The uni-directional constant light-dimming voltage Vdim or PWM light-dimming signal Vpwm provides the uni-directional light-dimming control to the LED string 30A by the 0-10 volt dimming control interface.
Reference is made to FIG. 2 which is a schematic block diagram of the related art light-emitting diode driver system of a second embodiment. The major difference between the second embodiment and the first embodiment is that the LED driver system can provide a bi-directional light-dimming control. Therefore, the LED driver circuit 20A is a digital addressable lighting interface (DALI). The bi-directional constant light-dimming voltage Vdim generated from the light-dimming control conversion unit 10A provides the bi-directional light-dimming control to the LED string 30A by the DALI.
In the both first embodiment and second embodiment, the control signal has to be converted into the specified signal of DALI, 0-10 volt, or PWM, and then the converted signal is provided to control the current signal at the output side (LED side). Because the control interfaces are separated and isolated, and the light-dimming signal is converted by multiple converters, such as PLC to DALI, or PLC to 0-10 volts, the losses are increased and the conversion efficiency is reduced. In addition, the size and occupied space are increased and the costs are also increased because the conversion circuits are installed. Furthermore, the additional circuit wires and increased working hours are unavoidable because the light-dimming control conversion unit 10A is externally connected to the LED driver circuit 20A.
Accordingly, it is desirable to provide an integrated light-emitting diode driver circuit and a method of operating the same to implement the bi-directional light-dimming function, the absence of the DALI dimming control interface or 0-10 volt dimming control interface, the reduced size and occupied space, lower costs, and higher conversion efficiency.